Electrical apparatuses operable by means of a commercial power source have a power supply unit for supplying electrical power from the commercial power source to the inside of the apparatus. Further, some electrical apparatuses have a secondary battery which is charged by electrical power supplied from a power supply unit and supplies electrical power to the inside of the apparatus.
Japanese Unexamined Patent Publication No. 2003-150281 (Patent Document 1) discloses an example of an electrical apparatus having a power supply unit and a secondary battery. In the electrical apparatus of Patent Document 1, by optimizing power consumption of the power supply unit and the secondary battery, reduction of power supply from the power supply unit is realized in a time period of large power demand (for example, for three hours from 1. p.m. to 4 p.m.). Specifically, Patent Document 1 shows a computer device as an example of an electrical apparatus, and describes that the computer device performs control as shown below.
The computer device is constituted of some sub systems including a CPU, a hard disk, and an inverter. At the start time of a peak power reduction time period (for example, 1 p.m.), the entire sub systems constituting the computer device transit to a first stage where electrical power is supplied from the secondary battery. Then, a retaining time of the secondary battery is calculated from the discharging current value of the secondary battery and the remaining capacity of the secondary battery, and it is determined whether or not the secondary battery is retainable until the end time of the peak power reduction time period. If the secondary battery is retainable, the first stage is maintained, but if not, the stage moves to the next stage, that is, a second stage.
In the second state, the power source of any of the sub systems (for example, inverter) is changed from the secondary battery to the power supply unit so as to reduce the discharging current value of the secondary battery. Then, a retaining time of the secondary battery is calculated from the discharging current value of the secondary battery and the remaining capacity of the secondary battery, and it is determined whether or not the secondary battery is retainable until the end time of the peak power reduction time period. If the secondary battery is retainable, the second stage is maintained, but if not, the stage moves to the next stage, that is, a third stage.
In the third state, the mode of the CPU is changed to a low-speed mode so as to further reduce the discharging current value of the secondary battery. Then, a retaining time of the secondary battery is calculated from the discharging current value of the secondary battery and the remaining capacity of the secondary battery, and it is determined whether or not the secondary battery is retainable until the end time of the peak power reduction time period. If the secondary battery is retainable, the third stage is maintained, but if not, the stage moves to the next stage, that is, a fourth stage.
In the fourth stage, the power source of the CPU is changed from the secondary battery to the power supply unit so as to further reduce the discharging current value of the secondary battery. At the same time, the mode of the CPU is returned to the normal mode from the low-speed mode. Then, a retaining time of the secondary battery is calculated from the discharging current value of the secondary battery and the remaining capacity of the secondary battery, and it is determined whether or not the secondary battery is retainable until the end time of the peak power reduction time period. If the secondary battery is retainable, the third stage is maintained, but if not, the stage moves to the next stage, that is, a fifth stage (final stage).
In the fifth stage, the power sources of the entire sub systems of the computer are changed to the power supply unit.
As another art related to the present invention, Japanese Unexamined Patent Publication No. 2006-230147 (Patent Document 2) discloses a power receiving system. The power receiving system is a system for controlling electrical power of the entire facility of a factory or a household having various electrical apparatuses such as lightings, air conditioners, and electronics devices. The system includes an AC power storage means, a switching means for switching between the AC power storage means and a commercial power, and a control device which detects received power energy and controls the switching means. The power receiving system uses only commercial power as a power source when the entire load on the facility does not exceed the contracted power energy, and when the received power of the facility is about to exceed the contracted power energy, the system supplies the deficient power energy of the received power with respect to the load, from the AC power storage means. Thereby, the power energy received from the commercial power source is suppressed to the contracted power energy or less. Further, when the peak power consumption time period has been passed and the entire load remains within the contracted power energy, power is supplied to the entire load on the facility while charging the AC power storage means by the received power. With this configuration, as there is no power consumption due to discharging from the AC power storage means in a time period other than the peak power consumption time period, the AC power storage means can be charged for peak power consumption of the next day.    Patent Document 1: JP 2003-150281 A    Patent Document 2: JP. 2006-230147 A
The electrical apparatus of Patent Document 1 is directed to reducing received power consumption in a time period of large power demand (for example, three hours from 1:00 p.m. to 3:00 p.m.). However, the invention of Patent Document 1 includes a fifth stage at which the electrical power for all of the subsystems of the computer are solely supplied from the power supply unit and the CPU is operated in a normal mode, and fails to have a system for suppressing the received power consumption in a time period other than the above-described tome zone. As such, the power supply unit is required to have a capacity capable of supplying power for the maximum power consumption of the entire electrical apparatus by itself.
Meanwhile, the power receiving system of Patent Document 2 is configured such that when it is detected that received power is about to exceeding the contract power, deficiency in the received power with respect to the load on the facility is supplied from the AC power storage means. As such, the power energy of the entire facility, received from the commercial power source, can be suppressed to the contracted power or less. However, there is no system for suppressing received power of each electrical apparatus in the facility to be a certain value or less. As such, the power supply unit in each of the electrical apparatuses is naturally required to have a capacity capable of supplying power for maximum power consumption of the electrical apparatus by itself.
In general, a power supply unit becomes larger as the maximum power supply capacity becomes higher, and also, the price becomes higher. Further, in a power supply unit, conversion efficiency of the power source deteriorates in an environment where the required capacity is significantly lower than its maximum power supply capacity. Generally, in an electrical apparatus, a time period in which it operates at maximum power consumption is not so long, and is typically operates in a state where power consumption is significantly lower than the maximum power consumption. As such, the power supply unit, capable of sufficiently covering the maximum power consumption of the electrical apparatus, operates in a state where the power efficiency is wrong for a long period in the operating time.